RU2388715C1 - Dry construction mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to decorative construction materials designed for protecting equipment and people in medical, industrial, scientific, administrative and residential facilities from the effect of ionising radiations. The dry construction mixture contains the following in wt %: caustic magnesite powder 10-15, barite concentrate 80-89, modifying additive 0.1-0.5, natural modification schungite III mineral - the rest. The invention is developed in subclaims.

EFFECT: design of material which provides efficient protection from gamma-radiation with reduction of the thickness of protective material and improvement of construction properties of the material at the same time.

6 cl, 2 tbl, 4 ex

Description

The invention relates to finishing building materials intended for the protection of technical equipment and people in medical, industrial, scientific, administrative and residential premises from exposure to ionizing radiation.

Known dry building mix according to the patent of the Russian Federation for the invention No. 2233255 from 01.29.2003 (prototype), which includes, wt.%:

caustic magnesite powder (MgO) 15-40 modifying additive 0.5-10 natural mineral shungite III species rest

The mixture is mixed with an aqueous solution of bischofite (MgCl ₂ ) and used for applying in the form of plaster or flooring on the inner or outer surfaces of the shielded room. After the curing of the mixture, durable, monolithic surfaces of building structures with conductive properties are obtained that provide protection against electromagnetic radiation, while the shielding efficiency, depending on the thickness of the material layer, is up to tens of decibels.

However, this mixture does not provide effective protection against ionizing radiation.

It is known to use barite aggregate for protection against gamma radiation, for example, as a component of plaster for the walls of x-ray laboratories. One of these compositions is described in the patent of the Russian Federation for invention No. 2029399. The construction mixture used in construction to protect against gamma radiation is concrete, which contains cement in the form of a binder and aggregates in the form of sand, gravel, as well as aggregates in the form of barite, or mortar (cement, barite and plasticizer). The disadvantages of such a composition include:

- shrinkage cracks;

- low strength characteristics;

- dust formation;

- poor adhesion to the bases (applied to the wall using a metal mesh);

- a long and laborious technological process of plastering - layer-by-layer application of 5-8 mm to the desired thickness with drying and priming of each layer;

- exposure to wet plaster for 2-3 days;

- grinding after drying;

- instability of attenuating properties when mixing components (cement with barite) directly on the construction site.

The objective of the present invention is to increase the effectiveness of protection against gamma radiation while reducing the thickness of the layer of protective material and improving its building properties.

The invention consists in the following. The dry building mixture contains caustic magnesite powder (as a binder), a modifying additive and the natural mineral shungite III modification. The mixture additionally contains barite concentrate as a filler in the following ratio of components, wt.%:

caustic magnesite powder 10-15 barite concentrate 80-89 modifying additive 0.1-0.5 natural mineral shungite III modification rest

Barite concentrate is used depending on the task of the following modifications: KB-3 (90% BaSO ₄ ), KB-5 (85% BaSO ₄ ) or KB-6 (80% BaSO ₄ ). In some specific conditions of use, barite concentrate can be supplemented with other types of filler in an amount of 0.5-5 wt.%, For example, building sand with fractions of 0.1-0.63 mm, marble or dolomite flour with a particle size of 0.1-0.315 mm

The finely ground natural mineral shungite of the III modification used in the proposed mixture has a particle size of 20-40 microns. Schungite rocks of III modification are characterized by high mechanical compressive strength (800-2000 kg / cm ² ), high density (2.35-2.45 g / cm ³ ) and low porosity (not more than 0.5%).

Owing to the presence of mineral phases of various nature of polarity (polar silicate and non-polar carbon phases), shungite III modification is well combined with all inorganic binders (cement, lime, water glass, gypsum, anhydrite, etc.).

Modifying additives serve to impart a mixture of various consumer properties, depending on the conditions of the particular application of the mixture. As modifying additives in an amount of 0.1-0.5%, preferably 0.1-0.3% by weight of the mixture can be used:

a polymer redispersible powder, for example, homo and copolymers of vinyl acetate, ethylene, vinyl laurate, or vinyl versalate;

- a component containing active silica microsilica or silica flour;

- a stabilizing and water-retaining additive, which can be used as a water-soluble modified cellulose ether methyl hydroxyethyl;

- a water-reducing additive, which can be used as a superplasticizer - a salt of sulfonated naphthalene formaldehyde or melamine formaldehyde polymers;

- anti-foaming additive, which can be used antifoam - a mixture of fatty hydrocarbons and polyglycols on an inert carrier - amorphous silica.

The mixture can be enhanced with iron oxide powder in an amount of 0-5 wt.%.

Caustic magnesite powder, which contains a mass fraction of active magnesium oxide from 0.75 to 0.95, was used as a binder component in the proposed mixture. For this, caustic magnesite powders are used in accordance with GOST 1216-87.

The proposed composition of the mixture provides an effective attenuation of ionizing radiation of a wide range of radionuclides with a smaller layer thickness than known building materials.

The manufacturing technology of dry building mixes includes the following operations: preparation, dosing and mixing in a mechanical mixer of caustic magnesite powder, barite concentrate, sand, schungite, iron oxide and modifying additives, followed by packaging in 20-25 kg paper bags.

Ready dry mixes are delivered to construction sites in dry form and mixed in a certain proportion immediately before use with natural bischofite - saline solution of magnesium chloride MgCl _{2 with a} density of 1.1-1.25 kg / l.

This composition is used for the manufacture of gamma radiation protective plasters (floor screed) with a compressive strength of 15 (25) MPa, respectively, after 28 days from the beginning of hardening.

Thus, in the present invention, the task of creating high-tech special dry building mixtures, which are manufactured in the factory, have stable protective properties and optimal performance characteristics. The above characteristics include: high strength, fast hardening rate, lack of porosity, non-shrinking (crack resistance), high adhesion to various building materials, incombustibility, and the absence of harmful emissions into indoor air. The mixture is smoothed and leveled until hardening is complete and does not require further grinding.

Table 1 shows the results of an experimental assessment of the protective properties of the proposed mixture with a thickness of 10 mm, which was used as a layer of plaster (floor screed) in the energy range from 1.25 to 0.06 MeV.

Table 1 Radionuclide The magnification of the attenuation of magnesia-barite composition (thickness 10 mm) Cobalt - 60 1.37 Cesium - 137 1.09 Sodium - 22 1.22 Barium -133 1.80 Cobalt - 57 5.00 Americii - 241 10.00

As table 1 shows, with a layer thickness of 10 mm, the proposed composition attenuates the emissions of various radionuclides from 1.09 to 10 times. With increasing layer thickness, the attenuation efficiency increases. The estimated estimate for the thickness of the layer of magnesia-barite composition is 28 mm - from 1.27 to 63 times, respectively.

Table 2 shows the calculated estimation of the required thickness of protection using magnesia-barite plaster in comparison with the known data on barite-concrete plaster (on Portland cement).

table 2 Lead equivalent Magnesia-barite plaster (on KB-5) Lead equivalent Barite-concrete plaster 1.0-1.4 mm Pb 15.4 mm 1.0 mm Pb 20-25 mm 2.0-3.0 mm Pb 19.7 mm 2.0 mm Pb 36-40 mm 3.0-4.0 mm Pb 24-28 mm 3.0 mm Pb 60-68 mm 4.0-6.0 mm Pb 34.6 mm 4.0 mm Pb 90 mm

The table shows the advantage in reducing the thickness of the layer of stucco samples from the proposed building mixture over barite-concrete composition, which gives a significant gain in cost, timing and weight of the building structure as a whole.

Plaster from the proposed building mixture can be used for leveling brick, concrete, plastered walls for subsequent painting, tiling, etc., as well as for repairing walls of existing premises. It is applied to the wall without using a metal mesh. Multilayer coating is allowed without drying and priming (wet on wet). The mixture hardens in about 40 minutes. Ready plaster does not require leaving (moisturizing) during the hardening process. A similar floor mixture can be used as a supporting floor screed with protective properties at the same time. The technical result of the use of magnesia-barite plaster (floor screed) is the ability to use them to protect against gamma and X-ray sources whose energy is equal to or less than 0.4 MeV. At the same time, an increase in the thickness of the lining by 3 times increases the efficiency of protection by 1-2 orders of magnitude in the energy range.

The proposed construction finishing material, due to the reliability and ease of working with it, environmental safety, can completely replace barite-cement compounds and lead protection.

The tests showed significant advantages of the proposed mixture over the known materials for solving the problem of protection against gamma radiation. Magnesia-barite plaster, in addition, has additional advantages:

- Does not accumulate static electricity.

- It is a non-shrinking, high-strength material, resistant to cracking.

- It is steady against rodents, a mold and a fungus - a micromycete.

- It has increased adhesion to any mineral substrates.

- Resistant to slipping.

- It belongs to the category of non-dusting and non-combustible materials.

- It can be used in unheated rooms.

The technology for producing the proposed dry building mix is illustrated by the following examples, in which silica fume is used as a modifying additive.

Example 1

Make up a mixture consisting of the following components, wt.%

caustic magnesite powder 10 KB-5 barite concentrate (85% BaSO ₄ ) 89 modifying additive 0.2 natural mineral shungite III modification 0.8

This composition has the best protective properties.

Example 2

Make up a mixture consisting of the following components, wt.%

caustic magnesite powder 10 KB-3 barite concentrate (90% BaSO ₄ ) 80 sand 5 modifying additive 0.5 natural mineral shungite III modification 4,5

This composition is more suitable for plastering and has increased resistance to slipping.

Example 3

Make up a mixture consisting of the following components, wt.%

caustic magnesite powder fifteen KB-6 barite concentrate (80% BaSO ₄ ) 80 modifying additive 0.5 natural mineral shungite III modification 4,5

This composition has better adhesion to various substrates.

Example 4

Make up a mixture consisting of the following components, wt.%

caustic magnesite powder 10 barite concentrate 80 dolomite flour 1,6 modifying additive 0.1 iron oxide 5 natural mineral shungite III modification 3.3

This mixture is elastic with sufficient strength.

After dosing, the components in dry form are mixed in a mixer and packaged in paper bags with a capacity of 20-25 kg. The finished mixture is already at a construction site mixed with saline bischofite with a density of 1.2 kg / l.

The application of the proposed composition of the dry mixture will provide effective protection for humans and equipment from gamma radiation.

Claims (6)

1. Dry building mixture containing caustic magnesite powder, a modifying additive and natural mineral shungite III modifications, characterized in that it additionally contains barite concentrate as a filler in the following ratio of components, wt.%:
caustic magnesite powder 10-15 barite concentrate 80-89 modifying additive 0.1-0.5 natural mineral shungite III modification rest 2. Dry building mix according to claim 1, characterized in that it contains barite concentrate KB-3. 3. The dry building mix according to claim 1, characterized in that it contains barite concentrate KB-5. 4. The dry building mix according to claim 1, characterized in that it contains barite concentrate KB-6. 5. The dry building mixture according to claim 1, characterized in that the filler is supplemented with sand, marble or dolomite flour in an amount of 0.5-5 wt.%. 6. The dry building mixture according to claim 1, characterized in that it further comprises iron oxide in an amount of 0-5 wt.%.